Electrode structure and method of manufacture



1946' w. M. TRUMBULL ET AL 2,413,267

ELECTRODE STRUCTURE AND METHOD OF MANUFACTURE Filed Nov. 25, 1942 U I3nncntors wQLTGR m liumaum E)! 6- UL Hangon Patented Dec. 24, 1946ELECTRODE STRUCTURE AND METHOD OF MANUFACTURE Walter. M. Trumbull,Newark, and Brice W. Kinyon, Bloomfield, N. J., assignors to RadioCorporation of America, a corporation of Delaware Application November25, 1942, Serial No. 466,866

7 Claims.

Our invention relates to electron discharge devices and particularly toimproved electrode structures for use in such tubes.

vMany electron discharge tubes, and particularly those of the cathoderay type, require an electron beam forming electrode structure which isrigid and in which the relative positioning of the electrodes ismaintained during life of the tube. Furthermore, .thespacingrequirements between electrodes of suchtubes are very critical so thatrelative movement of one electrode with respect to another, such as thecathode with respect to the grid, is detrimental to tube operation. Thusindirectly-heated cathodes in such tubes must be located with respect toan apertured control electrodevery accurately and must likewise retainthis positioning throughout tube life notwithstanding variations inoperating temperature-of the cathode. Such requirements for accuratespacing and rigidity have necessitated in :to accurate and rapidassembly in quantity'production, to provide a structurewherein-the'distance between the various parts is determined withoutreference tothe size of the parts and is maintained irrespective ofmechanical shock and temperature changes during use, -and.to provide amethod of assembly which is adaptedto high production at low cost andwhich may be followed by inexperienced assembly personnel,

These andother objects, features and advantages of our invention willbecome-apparent to those skilled in the art when considered in view ofthe following description and the accompanying drawing wherein:

Figure 1 is a plan view of a cathode ray tube incorporating ourimprovedelectrode structure;

Figure 2 is an expanded view of certain of the electrode structureshownin Figure l, and

Figure 3.is an electrode assembly .fixturesuitable for practicing ourmethod of electrode as- 'sembly.

Referring to Figure 1, wehave. showna cathode ray tube having'anenvelope I closed at oneend with a stem member 3 supporting, preferablyin .2 direct contact therewith, anelectron gun gen erally designated as5 to develop and direct an electron beam toward the opposite end of theenvelope I such as upon aluminescent-screen I.

In accordance with our. invention, .we provide ..a unitary electrode.assembly which may be assembled prior --to attachmentthereof to thesternor other support member .in the tube, the spacing of the various:partsbeing predetermined and fixed prior to its attachment but withoutreference to individual .part sizes .or tolerances. Where our electrodevassembly is .to beaflixed to the stem of the tube through which leadwires enter the envelope, .we .preferto use astem of the so-calledmeridian or button type wherein the lead wires are arranged inana-nnular .disposition.

Referring to-Figure 2, we have shown the stem member -3 as comprising anapertured disct'of glass having a centrally disposed closureor-exhausttube H. The disc S-suportsand is sealed to a number of lead wires ['3extending-through the disc and pref erably arranged annularly ab out andclosely within the periphery thereof. Preferably, the disc 9 isprovidedwithintegral-extensions or beads tEsurrOunding-each of the lead Wires.'In accordance-with our invention we provide a planar member extendingtransversely of the tube onwhich the electrodes comprising-the electrongun are rigidly-airlxed. Referringagain to Figure 2, our electrodestructure "comprising the heater, cathode and-grid is supported by aplanar insulating imembertl of sufiicient'thickness to'be substantiallyrigid vand'which isslo'tted "so'thatthe electrodes may be affixed to oneside thereof and'so that the:resu1ting assembly may beclosely-adjacentithe stem 3 preferably inscontact with and supported bythe beads [5 formed integrally with the stem disc '9. The insulating:member ll is provided with apertures having a'pluralityof "open-endedeyelets spatially aligned with the lead wires l'3'so that'the discmember thereto for the purpose of support and current conduction to theheater.

In the expanded view of Figure 2 we have shown the cathode and itssupporting structure directly above the heater 23 and aligned therewith.Preferably this structure in accordance with our invention comprises anouter cathode support cylinder '21 supporting an inner cylinder having aclosed end provided with electron emitting material which serves as thecathode 29, the two cylinders being maintained in longitudinal fixedrelation by a pair of cathode support straps 3|. These support straps 3|are preferably afiixed at their cathode ends on opposite sides of thecathode axis with the opposite ends aifixed to the cylinder 21 in amanner described below. The points of support on the cylinder 21 arepreferably out of line with the points of support on the cathode 29 sothat upon heating the cathode, axial longitudinal motion resulting fromexpansion is not imparted to the cathode. For this reason we prefer toaifix the cathode support straps 3| to the cathode closely adjacent itsupper end so that any expansion over the length of the cathode is in adownward direction. We prefer to provide a plurality of integralextensions on the cylinder 21 such as the three lugs 33 and likewiseprovide slots 35 in the planar insulating member I! into which the lugs33 may be fitted so that the end of the cylinder 21 abuts and is affixedto the member I! with the cathode 29 surrounding the heater 23.

The grid of our electrode structure preferably comprises a cylindricalmember 31 with its one end abutting the insulating member H and affixedthereto in permanent relation to the cathode support cylinder andcathode. Other electrodes may be supported by the grid cylinder throughceramic tubes 39 held to the grid cylinder by integral flanges 4|.Greater rigidity may be provided for the remaining electrodes by metalconductors 42 passing through the ceramic tubes 39 and affixed toeyelets 43 in the insulating member erably closed at its upper end withan apertured disc 45 and provided around its lower edge with lugs 41 sothat the cylinder may be rigidly attached to the insulating member llsuch as by passing the lugs 41 through the apertures or slots 49 in theinsulating member H.

In assembling our electrode structure the contact terminals 25 are firstafiixed to the insulating member I! and the legs of the heater 23 weldedor pinched to these conductors so that the heater is supported in anupright position with its axis normal to the member H. A mountingfixture such as shown in Figure 3 is then utilized to provide the properspacing between the upper end of the cathode 29 and the apertured griddisc 45 irrespective of large variations in part dimensions ortolerances. Referring to Figure 3, the fixture shown comprises a mandrel59 of relatively large diameter provided with a tip or arbor portion 52of reduced diameter substantally equivalent to the inside diameter ofthe cathode 2'9. The mandrel 50 is surrounded by two collars 54 and 56,the collar 54 being free to rotate about the mandrel 50'. Furthermore,one surface of the collar 54 is utilized as a reference surface and isprovided with apertures or slots corresponding in position about theaxis of the mandrel and arbor to the slots 35 and 49 in the insulatingmember H which correspond to the positioning of the lugs 33 and 41 Thegrid cylinder 31 is pref* on the cathode support cylinder 21 and gridcylinder 31 respectively. The second collar 55 is provided with a setscrew 58 so that it may be locked or secured to the mandrel 50 at anyposition along its axis. The collar 54 is provided with a cylindricalsleeve 66 having an external diameter approximately equal to theinternal diameter of the cathode support cylinder 21 minus the thicknessof the two cathode support straps 3|, and an internal diameter largerthan the diameters of the cathode 29 and the arbor 52. In addition, thesleeve 60 is provided with a pair of oppositely disposed slots orrecesses 62 corresponding in position to the desired location of thecathode support straps 3|.

Prior to assembly of the electrode structure utilizing the fixture ofFigure 3, we affix the cathode support straps 3| at one end to thecathode 29 and slip the cathode over the arbor 52 so that the straps 3|lie in the recesses 62. The cathode support cylinder is then seated onthe collar 54 with the lugs 33 in the corresponding slots. A spacer 64is then prepared having a thickness corresponding exactly to the desiredcathode-apertured grid disc spacing which is placed over the end of thecathode. The grid cylinder 37 carrying the grid apertured disc 45,preferably welded thereto, is then slipped over the sleeve 60 and thelugs 41 slipped into the corresponding slots in the collar 54. The setscrew 53 in the collar 56 is then loosened to allow the mandrel 50 andarbor.52 to be pushed forward holding the spacer 64 in firm contactbetween the cathode 29 and the apertured grid disc 45, following whichthe set screw 58 is again secured to the mandrel 50. This operationeffectively spaces the cathode with respect, to the apertured grid discwhile at the same time seating the ends of the cathode support cylinder21 and grid cylinder 31 in flush relation on the collar 54. Followingthis assembly operation, the ends of the cathode support straps 3|opposite the cathode are aflixed to the cathode cylinder 21. Thisoperation may be performed by providing the sleeve 60 as one electrodein a welding circuit and welding the straps 3| to the cathode supportcylinder 21. The parts thus accurately spaced may be removed from themounting fixture, the spacer 64 discarded for 50 future use and theparts assembled on the insulating member I! previously provided with theheater 23. Since the surface of the collar 54 conforms to the surface ofthe member H, the

parts are accurately spaced on the member ll 55 by slipping the lugs 33and 41 through the corresponding slots 35 and 49 in the member so -thatthe lower edges of the cylinders 21 and 31 are in the same spatialrelationship as when on the collar 54 such as flush and in contact with60 the member |1, whereupon the lugs may be bent over or twisted topermanently secure the cylinders to the insulating member followed byaffixing the conductors 42 to the eyelets 43 and assembly of theremaining electron gun parts 65 thereto.

The cathode and grid structure assembled with the insulating member I1is then fastened to the stem 3 by slipping the eyelets IS, previouslyaffixed to the member l1, over the correspondingly positioned lead wiresl3, whereupon the collar portion 2| of the eyelets may be welded to thecorresponding lead wires. Preferably a series of apertures correspondingin number and position to the lead wires are provided in the insulatingmember I! so that when this member carrying the cathode grid assembly isslipped over the lead wires, the insulating member H abuts and is heldsecurely against the heads [5 of the stem.

In this final assembly operation it will be noted that the lower edgesof the cathode support cylinder and grid cylinder occupy an identicalposition as previously occupied against the collar 54 of the Figure 3fixture. Consequently, the relative spacing between the cathode andapertured grid cylinder will be the same and correspond exactly to thethickness of the discarded spacer 64. It will be further appreciatedthat the straps 3| being afiixed to the cathode adjacent the spaced endwill provide a minimum portion of the cathode free to expand in an axialdirection when heated. Any expansion of the straps 3! will tend torotate the cathode about its axis, but such expansion will not causerelative displacement of the cathode along its axis. Consequently, thecathode remains in a fixed axial position notwithstanding variations inoperating temperature, and the spacing between the oathode and aperturedgrid disc will be constant during use.

From the foregoing description it will be ap preciated that our improvedconstruction provides a rigid structure including the ceramic tubes 39to which the other electrodes of the mount structure may be assembled.For example, referring to Figure 1, which shows the mount structureassembled in th envelope l, the first anode is provided with flangesafiixed directly to the ceramic tubular rods 39. The second anode discs12 and 14 are similarly afiixed to the tubular rods 4| which likewisesupport the conventional deflection plates 16 and 18. Furthermore, itwill be appreciated that the resulting mount structure is rigid and willwithstand the usual shocks and abuse during use of the tube.

We claim:

1. An electrode assembly for an electron discharge device comprising aplanar insulating member, a cylinder having one end abutting one side ofsaid member and having lugs extending therethrough and clinched againstthe opposite side thereof, a. cathode, straps having one of their endssecured to said cathode near the end thereof opposite that abutting saidmember and the other one of their ends secured to said cylinder, 2.second cylinder surrounding said first cylinder and having one endabutting the said one side of said member and having lugs extendingtherethrough and clinched against the opposite side thereof and anapertured disc in said second cylinder with the aperture aligned withsaid cathode.

2. An electrode assembly for an electron discharge device comprising amulti-apertured planar member, a cylinder having one end abutting saidmember and having tabs thereon extending through the apertures of saidmember, a tubular cathode having one end closed, arms secured to saidclosed end and to the said cylinder to support the cathode eoaxiallywithin said cylinder, a second cylinder of larger diameter than saidfirst cylinder having one end abutting said member and having tabsthereon extending through other apertures of said member and surroundingsaidfirst cylinder, an apertured element supported in the end of saidsecond cylinder 0pposite said member and a heater within said cathodehaving its end conductors extending out the open end of the cathode andthrough openings in said disc and back through other openings in saiddisc, whereby it is supported directly by said member.

3. An electrode assembly comprising an insulate ing disc having openingsextending therethrough, a hollow cylinder having an end edge normal toits axis with lugs extending through said openings and deformed to holdsaid edge against a side surface of said disc, a second hollow cylindersmaller than the first cylinder having an open end and a closed end,electron emitting material on the outside surface of said closed end,and arms having one of their ends secured to the smaller cylinderadjacent its closed end and the other of their ends secured to thelarger cylinder adjacent the end remote from said disc and arranged toposition the smaller cylinder coaxially within the larger cylinder.

4. An electrode assembly comprising an insulating disc having openingsextending therethrough, a hollow cylinder having an end edge normal toits axis with lugs extending through said openings and deformed to holdsaid edge against a side surface of said disc, a second hollow cylindersmaller than and within the first cylinder having an open end and aclosed end, electron emitting material on the outside surface of saidclosed end, and arms having one of their ends secured to the smallercylinder adjacent its closed end and the other of their ends secured tothe inner side of said larger cylinder adjacent the end remote from saiddisc with the open end of the smaller cylinder spaced from said disc.

5. An electrode assembly comprising an insulating disc having openingsextending therethrough, a hollow cylinder having an end edge normal toits axis with lugs extending through said openings and deformed to holdsaid edge against a side surface of said disc, a second hollow cylindersmaller than and within the first cylinder having an open end and aclosed end, electron emitting material on the outside surface of saidclosed end, arms having one of their ends secured to the smallercylinder adjacent its closed end and the other of their ends secured tothe inner side of said larger cylinder adjacent the end remote from saiddisc with the open end of the smaller cylinder spaced from said disc,and a heater having its end conductors extending out the open end of thecathode and through openings in said disc and back through otheropenings in said disc, whereby it is supported on said disc andextending into the smaller cylinder.

6. An electrode assembly comprising an insulating disc having openingsextending therethrough, a first and a second hollow cylinder, eachhaving an end edge normal to its axis with lugs extending through saidopenings and deformed to hold each of said edges against a side surfaceof said disc, with the second cylinder inside the first cylinder andspaced therefrom, a third hollow cylinder having an open end and aclosed end, electron emitting material on the outside surface of saidclosed end, arms having one of their ends secured to the third cylinderadjacent its closed end and the other of their ends secured to thesecond cylinder adjacent the end remote from said disc, and a .membersecured to the unattached end of said first cylinder having an aperturesubstantially in line with the axis of the third cylinder and spacedfrom the closed end thereof.

7. An electrode assembly comprising an insulating disc having openingsextending therethrough, a first and a second hollow cylinder,

side surface of the third cylinder adjacent its 10 closed end and theother of their ends secured tangentially to the inside surface of thesecond cylinder adjacent the end remote from said disc,

and a cap secured to the unattached end of said first cylinder having anaperture of less area than the electron emitting material on said closedend and aligned with the axis of the third cylinder.

WALTER M. 'I'RUMBULL. BRICE W. KINYON.

